A preliminary study of the killing function in vitro by T lymphocytes activated by dendritic cells loaded with exosomes secreted by hepatic cancer cell lines with high or low metastatic potentials

OBJECTIVE: To study the tumor cell killing function of T lymphocytes stimulated by dendritic cells (DC) and to analyze the differences of protein contents of exosomes in each type of cell. METHODS: The exosomes of hepatic cell lines with high (P group) or low (F group) metastatic potentials were isolated by a process of four-step centrifugation and the collected exosomes were observed under an electron microscope (EM). The tumor cell killing experiment was performed by adding T lymphocytes activated by DC loaded with exosomes from corresponding P and F group cells and was studied using 3H-TdR experiments. The proteomic analysis was performed by surface-enhanced laser desorption/ ionization time of flight mass spectrometry (SELDI-TOF-MS ) on the exosomes of P and F group cells. RESULTS: The density distribution and content of exosomes in the P group were not equal to those in the F group observed by EM. The CD80, CD86, MHC-I and MHC-II in the P group were 64.27+5.00, 44.89+10.11, 84.35+19.89 and 59.03+19.37, and those in the F group were 71.53+4.85, 50.01+9.50, 80.68+29.87 and 58.86+21.11, respectively (P>0.05, compared with the control group). The counts per minute value in the P group was 528.40+179.06 and 78.80+24.44 in the F group after being loaded with exosomes (P<0.01, compared with the control group). There were significant differences between the proteins in the exosomes of hepatic cancer cell lines with high or low metastatic potentials. CONCLUSION: Exosomes have potential values of application in immunotherapy and in biotherapy for recurrences and metastases of hepatic carcinomas.